@collindavenport,
Thanks for sending over the files! From our perspective, the vehicle definition has some issues. Before we dig into it, are you manually driving this vehicle (with the keyboard or joystick)? If programmatically controlled, can we get the code you are using to test out the vehicle?
On the vehicle def:
The FDS values are way too high, which causes the vehicle to slide around like crazy when doing any sort of steering.
One key point to note here is that the testers of these vehicles (generating the acceleration curves) are highly talented drivers that balance wheel spin off the line with throttle application. How the test is performed (is the throttle floored at the start? Is a clutch used to keep starting revs high and then blended in precisely?) will impact the results. You nor I could achieve this same acceleration curve in real-world driving without lots and lots of practice. Furthermore, in an ideal case, tires are warmed up, its on a very sticky bit of asphalt, etc, so we don't necessarily think tuning it to maximum performance with a simple vehicle controller is realistic.
It is extremely difficult to avoid spinning out the rear wheels on a car like the Demon. You have to baby the throttle as the torque is can provide in 1st gear is well beyond the traction limits of any tire.
Pacejka VTI will be the most accurate for pavement acceleration tests, and getting some more accurate tire data will be key to matching these super car results. Their tires have much higher peak grip than a standard road tire, and are super wide, which influences the slip/grip curves.
It looks like you are doing a trick of including a separate vehicle object to represent the center of mass, which slightly decreases processing performance, and may influence accuracy as well. It looks like you also included some debugging physics objects that are meant to represent the current wheel rotation rates. This is most likely actively interfering with the dynamics, and should be completely removed.
Hope this helps provide some insight...
Regards,
ANVEL Support